The Collaborative International Dictionary of English v.0.48:
Senile \Se"nile\, a. [L. senilis, from senex, gen. senis, old,
an old man: cf. F. s['e]nile. See Senior.]
Of or pertaining to old age; proceeding from, or
characteristic of, old age; affected with the infirmities of
old age; as, senile weakness. "Senile maturity of judgment."
Senile gangrene (Med.), a form of gangrene occuring
particularly in old people, and caused usually by
insufficient blood supply due to degeneration of the walls
of the smaller arteries.